Noise generated by vehicles has become of increasing concern, in recent years, in its effect both inside and outside the vehicle. Although the noise contributed by heavy-duty automatic transmissions in on- and off-highway vehicles is insignificant in relation to that generated by other vehicle components, a program was initiated to investigate sources and causes of transmission noise and to
develop methods of reducing or eliminating that noise.
In power transmission, the most common source of noise is vibration of individual gears in mesh. Two methods of decreasing gear mesh vibration have been found successful: improving gear tooth profile and counterphasing planetary gearing.